Light transmission measurement of solute dispersion in non-Brownian suspension flow

Grupo de Medios Porosos and CONICET, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, 1063 Buenos Aires, Argentina

^a e-mail: aboschfi@gmail.com

Received: 22 July 2013
Revised: 1 October 2013
Accepted: 22 October 2013
Published online: 6 January 2014

Abstract

We characterize and employ a light transmission technique to measure the dispersivity of a solute in the flow of a neutrally-buoyant non-Brownian spherical particle suspension in a Hele-Shaw cell (parallelplate axial flow). Particle radii (a) were 20 and 40 μm, the particle bulk volume fraction ϕ_bulk was 0.2, and the cell aperture was 420 ± 10 μm. In each displacement experiment a suspension with a colouring solute displaces a transparent one at constant flow rates ranging from 0.721 to 0.928 mL/min (corresponding to solute Péclet numbers (Pe_s) between 350 and 450). A reference measurement, identical to the displacement ones but without particles in the flow (ϕ_bulk = 0), were performed in the same experimental assembly for comparison purposes. A light calibration related the transmitted intensity I to the solute concentration c for each combination of ϕ_bulk and a. The time variation of the solute concentration was found to be well-fitted by the solution of the advection-dispersion equation (ADE) in the range of Pe_s studied, and consequently a dispersion coefficient D and a dispersivity l_d of the solute were measured.